Dental decay is the most prevalent affliction in children worldwide. In recent years the occurrence of dental decay has declined dramatically in many industrialized countries subsequent to the wide spread availability of fluoride in the water supply and dentifrices. However, in newly industrialized countries such as Brazil, the occurrence of decay is still high, especially among lower income groups. The mutans streptococci (MS) have been convincingly associated with human dental decay, and clinical protocols which seek to reduce the levels of the MS invariably result in a significant reduction in decay. One of the most important observations from these studies is the possibility that decay and the establishment of MS can be reduced and/or prevented in young children by treating those mothers who are highly infected with MS prior to the eruption of the primary teeth. Other studies indicate that if the primary teeth are not colonized by the MS in the first year after their eruption, they are likely to remain caries free, during the following years. These findings indicate that dental decay may be prevented by delaying the colonization of the MS in primary dentition. The ideal population for such a study could be found in communities without water fluoridation, with a high level of unmet dental care, and who would have frequent access to sugar. Populations in many newly industrialized countries would meet these qualifications. However, it is difficult to perform an interceptive study, such as preventing the transmission of the MS from mother to infant in such countries, as the local dental community has neither the financial and physical resources nor the trained dental personnel. We have found an exception to this in the city of Bauru, Sao Paulo, Brazil. This community of 250,000 residents is situated in the sugar cane growing region of Brazil and boasts the leading dental school in South and Central America. In the investigation to be described, we will collaborate with the Bauru investigators in a longitudinal randomized clinical trial with the following specific aims: 1) to determine whether the salivary levels of the MS can be reduced in mothers of young infants by an intervention program which may include restorative procedures, topical fluorides, the use of xylitol chewing gum, and chlorhexidine varnishes; 2) to determine whether this intervention reduces or delays the acquisition of MS in the infants and whether this in turn reduces the subsequent caries incidence in children.